The present invention relates to excavation tools. In particular, the present invention provides a means of capturing and removing dirt debris and gravel debris from the bottom of cylindrical excavations used for construction footings by use of a cleaning tool or dredge which rotates to scrape together and capture the loose soil, sand and gravel debris at the bottom of the hole to provide a clean, flat-bottomed hole which is free of compressible excavation waste material.
In the construction of houses, buildings or deck structures added to houses, it is a common requirement that excavations for concrete footings be provided at spaced intervals to support the construction. The general types of footings that are used are spread footings, pad footings, and wood pier footings, and concrete column footings. Spread footings are simply a wide-base footing which is used to distribute the weight of the structure and foundation over a larger portion of the ground. In modern construction, a spread footing is usually 16-24 inches wide and 6-16 inches thick and made of poured concrete. The dimensions of the footing will vary according to the soil conditions under the structure and the amount of weight that is being placed on the footing and the construction style of the building.
Another type of footing is the pad footing. A pad footing is similar to a spread footing but it is usually limited to spreading the force or weight of a single support or contact point. A pad footing may be used under a pier or post and is typically a 2 foot by 2 foot square pad with a thickness of 10-12 inches. Pad footings are usually of poured concrete. In modern construction, pad footings are frequently used with lightweight decks and stable soil conditions.
The type of footing which is used with heavier buildings or buildings that are to be placed on unstable soils is concrete column footing. The concrete column footing is constructed by first drilling a cylindrical hole into the ground until rock or other suitable stable substrate is encountered. Such concrete piers are typically used in areas where other footing types are not desirable due to poor soil quality or where there is a high water table.
During the excavation of the cylindrical hole for the concrete pier, it is typical that an auger-type bit will be used to rapidly drill through the earth until bedrock or other suitable solid substrate is encountered. Once the hole has been drilled, it is necessary that the bottom of the hole be cleared of all loose sand, gravel and dirt, and that a clean, solid surface be presented for the concrete to contact. The removal of compressible soil and other drilling waste left behind by the auger is critical to a stable column footing. If the compressible dirt and waste is not removed from the excavated hole, this material will eventually compress after the concrete is poured into the hole. Such compacting of compressible materials may not occur immediately or completely when the concrete is poured into the hole and compression of the material and settling of the concrete pier may occur after construction has been completed. Such settling of the concrete pier can be disastrous to the construction resting upon the concrete pier. The settling of a concrete pier by even one-half inch could result in severe crack in a concrete basement floor or substantial settling of the structure residing on the concrete causing cracks in walls and jammed doors and windows.
For insurance purposes, and before concrete is poured into the hole, a soil engineer is usually consulted for approval of the holes. The engineer will inspect all holes before concrete is poured and make a mapped report on all hole depths, the number of piers, how clean the hole are at the bottoms, which holes were dug, the type of soil at the hole bottom, and the diameter of the piers. Before concrete is poured for the structure, all holes for piers must pass these daily inspections.
In the prior art, to clear such compressible debris from excavated cylindrical holes, it has been the typical procedure to clean out the compressible materials and debris by hand. For shallow and narrow holes, this has been accomplished by using a post hole digger or a long handled shovel which allows the worker to reach to the bottom of the hole and retrieve the loose dirt and other waste materials. In the case of larger diameter excavations, workers have been known to engage in the extremely unsafe practice of going down into the excavated footing hole to clear the loose dirt and compressible material by hand. This procedure is extremely dangerous as the sidewalls of the newly excavated hole are not supported by shoring of the walls. Such shoring is needed to prevent the collapse of the hole on a worker within the excavated hole. Many times a year, workers are suffocated to death by working in trenches which have not had any shoring applied to the sidewalls of the trench. This same type of collapse can occur with auger excavated holes intended for concrete piers. The risk of such a collapse should be avoided at all costs.
Yet another drawback of the conventional means of clearing compressible dirt and debris from the bottom of augured concrete pier excavation holes is the cost of accomplishing the cleaning of the hole. Depending on the size and depth of the hole, it can take a single person from 20-30 minutes to hand-clean the bottom surface of a hole. For example, it is possible using a 24-inch diameter auger attached to a skid-steer tractor to drill 21 footing holes six feet deep in well-packed clay within a five hour period of time. This period of time includes the moving of the loose dirt away from each hole and into a waste pier. A quickly working person hand-cleaning each hole would require approximately 20 minutes. For the 21 holes of the present example, nearly seven hours would be required to clean the holes. Therefore it can be appreciated that substantial time and cost is involved in cleaning the compressible debris from footing holes.
Yet another problem associated with hand-cleaning of dirt and compressible debris from footing holes is the time requirements associated with drilling the hole, cleaning the hole, and filling the hole with concrete. To minimize time and effort, it is preferred that the footing holes be drilled, cleaned and filled with concrete before the end of the work day. For practical purposes, this means that the holes must be drilled and cleaned prior to about 2 o""clock in the afternoon so the concrete can be scheduled to arrive and poured into the holes before it is time to quit for the day. If the augured footing holes are not filled with concrete prior to the end of the day, it is necessary for safety reasons to cover each hole with an immovable cover. Typically such a cover would be a 3 foot by 3 foot sheet of plywood, which is then weighted down by a mound of dirt to prevent children or others who might wander onto the construction site from removing the cover and falling into the hole and being trapped or buried in the hole should the sidewalls collapse. Therefore, a need exists for a device or tool which can be extended into the freshly auger-drilled footing hole to gather and capture the loose dirt and compressible debris which remains in the hole after it is drilled with a convention auger bit.
Further, a need exists for a device which can be inserted into a freshly augured hole to clean the compressible debris from the hole which can be rapidly and efficiently operated to reduce the time needed to scrape together the loose debris at the bottom of the hole and to provide a clean surface at the bottom of the hole for receiving concrete.
Further, a need exists for a tool which can be placed into a freshly augured footing hole which can be attached to the auger drilling device in place of or on the end of the auger bit and accomplish the cleaning of the hole utilizing the same device and personnel which was used to auger drill the hole.
The above problems are solved and needs fulfilled by the present invention which provides a circular plate having an opening therein and a scraper blade extending therethrough which can be lowered into an augured hole of the proper diameter and rotated therein to scrape together and capture the loose compressible dirt and material at the bottom of the hole. The plate may or may not have a sideall attached thereto which extends upwardly from the plate and serves as a retaining wall for assisting and capturing the loose dirt and material which has been scraped onto the plate during rotation of the plate in the hole and to allow the loose dirt and material to be withdrawn from the hole as the tool is withdrawn from the hole. It is a further benefit if the plate is provided with a replaceable and depth-adjustable blade as well as an adjustable plate which can be used to vary the size of the opening in the plate to allow greater or smaller amounts of material to be scraped up onto the plate and to reduce the amount of material which can fall back through the hole in the plate and into the floor of the excavated hole.
The foregoing and other objects are intended to be illustrative of the invention and are not meant in a limiting sense. Many possible embodiments of the invention may be made and will be readily evident upon a study of the following specification and accompanying drawings comprising a part thereof. Various features and subcombinations of invention may be employed without reference to other features and subcombinations. Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention.